The present invention relates to a backlash reducer applicable to a gear transmission system such as a valve-operating-camshaft driving system for transmitting power from an internal combustion engine to a camshaft through a gear train, for example.
A gear transmission system in general such as the above-mentioned valve-operating-camshaft driving system for an internal combustion engine has the disadvantage that a backlash rapidly increases an impact load due to fluctuation in torque applied to the gears, resulting in an increase in knocking sound or chattering and a damage to the gears due to an abnormal load caused by the resulting resonance of the transmission system.
In order to solve the above-described problem, a backlash reducer has been proposed in which at least one of a driving gear and a driven gear in mesh therewith is constituted by a main gear mounted on a rotary shaft for rotation therewith and an auxiliary gear mounted on the rotary shaft in coaxial relation to the main gear for rotation relative thereto. Springs are disposed between the main and auxiliary gears for biasing same in such a direction that the main and auxiliary gears are angularly moved relative to each other. The main and auxiliary gears are brought into mesh with the mating gear in such a manner that a tooth of the mating gear is clamped between a tooth of the main gear and an adjacent tooth of the auxiliary gear with the adjacent teeth of the respective main and auxiliary gears being biased toward each other by the springs, to thereby redeuce the backlash and absorb the impact force.
However, when in particular the torque increases, the backlash reducing effect of such conventional backlash reducer would be lost if the force of the springs is relatively weak as compared with the increase in the torque. In order to avoid this, should the spring force be strengthened, meshing noise would be generated when the torque is relatively low.
Thus, it has been difficult to ensure reduction in backlash over the entire range from a low rotational speed to a high rotational speed of a gear transmission system in which fluctuation in torque is considerably high, such as a gear transmission system for use in an internal combustion engine.